Sieve stage

FIG. 14-27 Weeping, sieve plates. To convert millimeters to inches, multiply hy 0.0394. (Smith, Design of Eqiihihiiiim Stage Processes, McGraw-Hill, New York, 1963.)... 

Dry-Process Cement After crushing, the feed may be ground from a size of 5 to 6 cm (2 to 2 /2 in) to apowder of 75 to 90 percent passing a 200-mesh sieve in one or several stages. 

A recently developed adsorbent version of ORNL s porous carbon fiber-carbon binder eomposite is named carbon fiber composite molecular sieve (CFCMS). The CFCMS monoliths were the product of a collaborative researeh program between ORNL and the University of Kentueky, Center for Applied Energy Researeh (UKCAER) [19-21]. The m.onoliths are manufactured in the manner deseribed in Section 2 from P200 isotropic pitch derived fibers. While development of these materials is in its early stages, a number of potential applieations can be identified. 

Figure 8-126. Aeration factor, sieve trays. Used by permission. Smith, B. D. Design of Equilibrium Stage Processes, Chapter 15, by J. R. Fair, McGraw-Hili Book Co. (1963), all rights reserved.

Figure 8-129. Discharge coefficients for vapor flow, sieve trays. Used by permission, Smith, B. O., Design of Equilibrium Stage Processes, Chapter 15, by J. R. Fair, McGraw-Hill Book Co. (1963) data from I. Liebson, R. E. Kelley, and L. A. Bullington, Petroleum Refiner, V. 36 (2), Feb. (1957) p. 127 V. 36 (3), (1957) pg. 288, all rights reserved.

Thus, a 20-foot baffle tray section, with 50% cut baffles on 24-in. spacing can contain 10 elements and produce 5.2 theoretical stages of separation. A corresponding crossflow sieve tray section, with 10 trays at 90% efficiency (16), can produce 9 theoretical stages. This ratio is about as expected. 

Trays are usually designed with F-factor from 0.25 to 2.0 for a turndown of 8 1. Pressure drop per theoretical stage falls between 3 and 8 mm Hg. Note that bubble cap trays are on the high side and sieve trays are on the lower end of the range. Varying tray spacing and system efficiency, the HETP for trays are usually between 24 in. and 48 in. [133]. The C-factor is the familiar Souders and Brown capacity equation. 

Characteristics of attrition and adsorption were investigated to remove CO2 in fluidized hed using activated carhon, activated alumina, molecular sieve 5 A and molecular sieve 13X. For every dry sorbent, attrition mainly still occurs in the early stage of fluidization and attrition indexs(AI) of molecular sieve 5A and molecular sieve 13X were higher than those of activated carbon and activated alumina. Percentage loss of adsorption capacity of molecular sieve 5A and molecular 13X were 14.5% and 13.5%, but that of activated carbon and activated alumina were 8.3% and 8.1%, respectively. Overall attrition rate constant (Ka) of activated alumina and activated carbon were lower than other sorbents. 

The presence of methylenic bands shifted at higher frequency in the very early stages of the polymerization reaction has also been reported by Nishimura and Thomas [114]. A few years later, Spoto et al. [30,77] reported an ethylene polymerization study on a Cr/silicalite, the aluminum-free ZSM-5 molecular sieve. This system is characterized by localized nests of hydroxyls [26,27,115], which can act as grafting centers for chromium ions, thus showing a definite propensity for the formation of mononuclear chromium species. In these samples two types of chromium are present those located in the internal nests and those located on the external surface. Besides the doublet at 2920-2850 cm two additional broad bands at 2931 and 2860 cm are observed. Even in this favorable case no evidence of CH3 groups was obtained [30,77]. The first doublet is assigned to the CH2 stretching mode of the chains formed on the external surface of the zeolite. The bands at 2931 and... 

Perhaps the most serious possibility for error at this stage of the sampling process Is In discarding of vegetation, sod, or other non-soil material collected along with the soil sample as well as the discarding of other materials retained on the sieve. It Is recommended that for approximately 10% of all samples where vegetation, sod, or other non-soil material Is discarded, all discarded material... 

Extractors with mechanical agitation, such as mixer-settlers, Kuhni columns, York-Schiebel columns, etc., should be avoided as much as possible. Up to seven theoretical stages packed extraction columns can be conveniently adopted. Sieve-plate extractors can be used up to 20 stages. When a very efficient extraction has to be carried out with expensive solutes, and for reasons of material stability and requirements of low expensive product inventory, we may have to use centrifugal extractors or hollow-fibre extractors. 

A wide variety of extraction column forms are used in solvent extraction applications and many of these, such as rotary-disc contactors (RDC), Oldshue-Rushton columns, and sieve-plate column extractors, have rather distinct compartments and a geometry, which lends itself to an analysis of column performance in terms of a stagewise model. As the compositions of the phases do not come to equilibrium at any stage, however, the behaviour of the column is therefore basically differential in nature. 

Sieve plates are used, similar to those used for distillation and absorption. The stage efficiency for sieve plates, expressed in terms the height of an equivalent theoretical stage (HETS), will, typically, range from 1 to 2.5 m. 

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